Balloons are good at providing substantially uniform forces to the walls of a body lumen because most such lumens have a circular cross-sectional profile, as do most balloons. Indeed, it is difficult to create a balloon that, upon inflation, assumes other shapes other than cylindrical shapes with circular cross-sectional profiles since such a shape generally minimizes wall tension by maximizing the ratio of volume to surface area.
A balloon's tendency to adopt a circular profile becomes a problem when the balloon is being used to apply force to a non-circular surface. Pressure is applied uniformly only when the shape of the impacted surface matches the shape of the balloon (i.e., circular). Many compressive applications, outside the bounds of a body lumen, call for balloons of fixed, non-circular, inflated shape.
Accordingly, balloons that may be expanded to non-circular profiles would be useful.